Semiconductor devices are used in a variety of electronic applications, such as personal computers, cell phones, digital cameras, and other electronic equipment, as examples. Semiconductor devices are typically fabricated by sequentially depositing several insulating or dielectric layers, conductive layers, and semiconductive layers of material over a semiconductor substrate, and patterning the various layers using lithography to form circuit components and elements thereon.
There is a trend in the semiconductor industry towards reducing the size of features, e.g., the circuits, elements, conductive lines, vias, and contacts of semiconductor devices, in order to improve the performance of the semiconductor devices, reduce power consumption, and meet smaller packaging requirements, for example. However, as feature sizes of semiconductor devices diminish, the patterning of features becomes more challenging. The transfer of patterns of lithography masks to semiconductor devices having small feature sizes may be inaccurate or unpredictable in some applications, for example.
Double patterning is a process that is used to print small minimum feature sizes of some semiconductor devices. In double patterning, a design for conductive lines is split into two layouts each having a minimum pitch equal to two times the minimum pitch of the original design. Two lithography masks are used to print alternating conductive lines, so that each mask can be imaged with better contrast due to the relaxed pitch. A patterning process flow for double patterning typically includes exposing a first resist film with a first lithography mask, transferring an image of the first mask from the first resist film into a hard mask, and stripping the first resist film. A second resist film is recoated and exposed with a second lithography mask, and the second resist image from the second lithography mask is transferred into the hard mask. The hard mask is then used as an etch mask to pattern a material layer beneath the hard mask.
Double patterning techniques may work well in some applications where the conductive lines are parallel along their entire length. However, double patterning presents problems such as shorts and misalignment in some designs, such as designs having meandering patterns, particularly when optical proximity correction (OPC) is used to improve pattern transfer, because minimum pitch and/or gap sizes can be reintroduced.
Thus, what are needed in the art are improved methods of patterning features of semiconductor devices.